The invention relates to a switchgear apparatus comprising a fixed frame and a circuit breaker which can be inserted in or extracted from the fixed frame. It relates more precisely to the circuit breaker designed for such a switchgear apparatus.
A switchgear apparatus of this kind is described in the document EP-A-0,227,586. Its circuit breaker comprises a pair of contacts per pole, one of the contacts being movable and able to take with respect to the other a closed position corresponding to mechanical and electrical contact, and an open position. The circuit breaker is equipped with an opening device of the poles comprising a spring called the opening spring designed to move from a loaded state to a released state and from the released state to the loaded state, and a latch called the opening latch designed to latch the opening spring in its loaded state, the opening spring being associated to the movable contact in such a way that releasing of the opening spring drives the movable contact to an open position and that movement of the movable contact to its closed position results in loading of the opening spring. The circuit breaker is moreover equipped with a closing device provided with an energy storage device. A spring called the closing spring, constituting the energy storage device, is designed to move from a loaded state to a released state. A latch called the closing latch can latch the closing spring in its loaded state. The closing spring is associated to the movable contact in such a way that releasing of the closing spring drives the movable contact to its closed position.
The frame comprises main terminals connected to the electrical power circuit, for example via an external busbar, and designed to operate in conjunction with the terminals of the circuit breaker poles via plug-in contacts. It also comprises auxiliary connectors designed to operate in conjunction with corresponding connectors of the circuit breaker to close an electrical control circuit of the circuit breaker. The frame is box-shaped and comprises an opening on the front panel enabling the circuit breaker to be inserted, as well as slides for support and guiding of the circuit breaker in the frame. The frame is provided with a kinematic engagement system comprising a primary shaft designed to operate in conjunction with a removable crank-handle and an output element designed to operate in conjunction with the circuit breaker. The kinematic system is designed to take a plugged-in position corresponding to a plugged-in state of the circuit breaker in which the circuit breaker terminals are secured to the corresponding terminals of the frame, a plugged-out position corresponding to a plugged-out state of the circuit breaker in which the latter is not connected to the frame either by these main terminals or by its auxiliary connectors, and an intermediate test position corresponding to a test state of the circuit breaker in which the latter is connected to the frame by its auxiliary connectors, whereas its main terminals are disconnected. When the kinematic system is in the plugged-out position, the circuit breaker can be unsecured from the kinematic system to extract it completely from the frame.
The circuit breaker is equipped with an opening control designed to ensure that the poles are open when the kinematic system leaves its plugged-in position or approaches the latter position. This function is essential for safety of the device. Indeed, if the circuit breaker poles were closed when plug-in or plug-out takes place and a voltage was applied to the connection terminals of the frame, a destructive electrical arc would occur between the circuit breaker connection terminals and those of the frame. For reliability reasons, this control must be mechanical in order to ensure correct operation even in case of failure of the electrical control circuits of the circuit breaker. This function is therefore performed by a control comprising a movable element connected by a linkage system to the opening latch and able to take information relative to the presence of the removable crank-handle driving the kinematic engagement system. So long as the crank-handle is in the active position, the movable element remains in a position such that it forces the opening latch to remain in its unlatched position.
Furthermore the circuit breaker described in EP-A-0,227,586 is equipped with a device which guarantees that the circuit breaker opening latch and closing latch are placed in their unlatched position so long as the apparatus is extracted from its frame. This device complies with the usage which requires in certain countries that handling operations enabling the circuit breaker to be extracted from its frame give rise to automatic sequences so that the circuit breaker at the end of the extraction phase is open and that its energy storage device is unloaded, in order to avoid any risk of accident for the operator having to perform handling or disassembly of the circuit breaker. In practice, the circuit breaker is equipped with an operating device comprising a lever designed to take information from a cam securedly affixed to the fixed frame of the apparatus, and a transmission system to transmit the movement of the lever to the closing and opening latches. In a first position of the operating lever, the latches are free to take their latched or unlatched position. In a second position of the lever, the transmission system forces the two latches to take their unlatched position. Return springs bias the operating lever to its second position. When the circuit breaker is in the fixed frame, the lever operates in conjunction with a cam securedly affixed to the fixed frame, which forces it to take its first position: the latches can then take their unlatched or latched position depending on the orders transmitted by other control devices of the circuit breaker. When the circuit breaker is extracted from the fixed frame to a position beyond its plugged-out position, the operating lever is no longer in contact with the cam of the frame and takes its second position due to the biasing force of the return springs, moving the opening latch and closing latch to their unlatched position.
But the usage described above is not universal for it comprises several drawbacks. It can be noted for example that extraction of the circuit breaker according to the sequence described above may give rise to discharge of the closing spring whereas the opening latch is kept in the open position. In such a cycle, called discharge on open poles or no-load discharge, the energy of the closing spring is completely absorbed by end of travel stops which, in conventional opening and closing cycles, only have to absorb ten times less energy. This imposes either costly oversizing or a compromise on the endurance of the device. Certain users therefore do not want extraction of the circuit breaker to give rise to forced unloading of the device and limit their requirements to opening of the poles when plug-out takes place. We are therefore confronted with two markets with different requirements, one imposing that the closing spring be unloaded at the end of extraction and the other imposing that extraction does not have any influence on whether the closing spring is in the loaded or unloaded state.
The device described in EP-A-0,227,586 is not easily adaptable to all the markets for which a range of circuit breakers is intended. For fitting of the opening and unloading control to be possible at an advanced stage of manufacture of the circuit breaker, the control elements must be placed on one of the side faces of the circuit breaker, which imposes additional constraints and makes the device vulnerable to knocks, in particular when extraction and removal of the circuit breaker take place In addition, the device is complex since it imposes a superposition of two mechanical opening controls, one designed for opening when plug-in and plug-out operations are performed, i.e. between the plugged-in position and the test position, the other for opening when extraction and insertion are performed, between the plugged-out position and the extracted position.